Introduction to Cranial Nerves

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1. Review the definition and characteristics of a cranial nerve.

Cranial nerves contain sensory and motor fibers or both that innervate muscles or glands, or carry impulses from sensory areas. They emerge through foramina in the cranium and are covered by tubular sheaths derived from cranial meninges. The twelve pairs of cranial nerves are numbered I through XII from anterior to posterior, according to their attachments to the brain.

Three cranial nerves are sensory, five are motor, and four are mixed sensory and motor. Four cranial nerves carry presynaptic parasympathetic axons as they emerge from the brainstem: CN III (oculomotor nerve), CN VII (facial nerve), CN IX (glossopharyngeal nerve), and CN X (vagus nerve). There are are no sympatheic afferents in cranial nerves.

The fibers of cranial nerves connect centrally to cranial nerve nuclei – groups of neurons in which sensory or afferent fibers terminate and from which motor or efferent fibers originate. Except for the olfactory areas of CN I, the nuclei of cranial nerves are located in the brainstem.

2. Review the components of a spinal nerve; describe the components of cranial nerves.

There are 31 pairs of spinal nerves that emerge from segments of the spinal cord and use intervetebral foramena to leave the vertebral column. They consist of mixed nerves with motor and sensory components that distribute to the skin, muscles of the trunk, and the upper and lower limbs.

There are 12 pairs of cranial nerves that emerge directly from the brain and use named foramena to leave the skull. They consist of mixed, sensory only, or motor only nerves that distribute to the skin and muscles of the neck.

3. Name the twelve cranial nerves.

Cranial Nerve	Nerve	Classic Dirty Mnemonic	Clean Mnemonic for Pansies
CN I	Olfactory Nerve	Oh	Oh
CN II	Optic Nerve	Oh	Once
CN III	Oculomotor Nerve	Oh	One
CN IV	Trochlear Nerve	To	Takes
CN V	Trigeminal Nerve	Touch	The
CN VI	Abducens Nerve	And	Anatomy
CN VII	Facial Nerve	Feel	Final
CN VIII	Vestibulococlear Nerve	Virgin	Very
CN IX	Glosspharyngeal Nerve	Girls'	Good
CN X	Vagus Nerve	Vaginas	Vacations
CN XI	Accessory Nerve	And	Are
CN XII	Hypoglossal Nerve	Hymens	Heavenly

4. For each cranial nerve, identify functional components and relative position in cranial vault.

All of the cranial nerves can be seen on the ventral aspect of the brain except for CN I and CN IV. CN I is in the mucous membrane of the nasal cavity and CN IV exists from the dorsal surface. The twelve pairs of cranial nerves are numbered I through XII from anterior to posterior, according to their attachments to the brain.

Cranial Nerve	Nerve	Origin Location	Components	Classic Dirty Mneumonic
CN I	Olfactory Nerve	Olfactory Mucosa	Sensory	Some
CN II	Optic Nerve	Ganglion cells of neural retina	Sensory	Say
CN III	Oculomotor Nerve	Midbrain (Mesencephalon)	Motor	Marry
CN IV	Trochlear Nerve	Midbrain (Mesencephalon)	Motor	Money
CN V	Trigeminal Nerve	Pons; sensory and motor root	Both Sensory and Motor	But
CN VI	Abducens Nerve	Junction of pons and medulla	Motor	My
CN VII	Facial Nerve	Junction of pons and medulla	Both Sensory and Motor	Brother
CN VIII	Vestibulococlear Nerve	Junction of pons and medulla	Sensory	Says
CN IX	Glosspharyngeal Nerve	Medulla	Both Sensory and Motor	Big
CN X	Vagus Nerve	Medulla	Both Sensory and Motor	Breasts
CN XI	Accessory Nerve	Cranial root emerges from medulla; spinal root emerges from superior part of spinal cord	Motor	Matter
CN XII	Hypoglossal Nerve	Medulla	Motor	More

Cranial Nerves			Motor Components			Sensory Components		Special Sensory Components
Nerve Number	Nerve Name	Motor Skeletal Muscle (Not from Arch)	Motor Skeletal Muscle (Pharyngeal Arch)	Motor Parasympathetic Smooth Muscle or Glands	Sensory Pain, Pressure, or Temperature	Sensory Pain from Organs or Mucous Membranes	Special Sensory Smell or Taste	Special Sensory Vision, Hearing or Balance
CN I	Olfactory Nerve						Smell
CN II	Optic Nerve							Vision
CN III	Oculomotor Nerve	Extraocular muscles		Pupillary sphincter, ciliary muscles
CN IV	Trochlear Nerve	Superior oblique muscle (one of extraocular muscles)
CN V1	Trigeminal Nerve – Ophthalmic				Skin of superior face: forehead, upper eyelid, temple, cornea
CN V2	Trigeminal Nerve – Maxillary				Skin of middle face: cheeks, upper teeth, nasal cavity, upper lip
CN V3	Trigeminal Nerve – Mandibular		Muscles of mastication		Skin of inferior face: lower teeth, chin, tongue
CN VI	Abducens Nerve	lateral rectus muscle (one of extraocular muscles)
CN VII	Facial Nerve		Muscles of facial expression	Lacrimal glands, mucous glands of nasal cavity, salivary glands of oral cavity	External ear		Taste of anterior 2/3 of the tongue
CN VIII	Vestibulococlear Nerve							Hearing and Balance
CN IX	Glosspharyngeal Nerve		Stylopharyngius muscle	Parotid gland (salivary)		Mucous membrane of the pharynx and posterior tongue	Taste of posterior 1/3 of the tongue
CN X	Vagus Nerve		Skeletal muscles of the palate, pharynx and larynx	Cardiac muscle, smooth muscle of thorax and abdomen, mucus glands in pharynx and larynx		Organs of thorax and abdomen and mucous glands from pharynx and larynx	Taste in area of the epiglotis
CN XI	Accessory Nerve	Sternocleidomastoid muscle, trapezius
CN XII	Hypoglossal Nerve	Intrinsic and extrinsic muscles of the tongue

5. Name and describe ganglia that are associated with the cranial nerves.

Cranial Nerve	Nerve	Ganglion	Foramen
CN I	Olfactory Nerve	Anterior Olfactory Nucleus	Cribiform Plate
CN II	Optic Nerve	Lateral Geniculate Nucleus	Optic Canal
CN III	Oculomotor Nerve	Oculomotor nucleus, Edinger-Westphal nucleus	Superior Orbital Fissure
CN IV	Trochlear Nerve	Trochlear nucleus	Superior Orbital Fissure
CN V	Trigeminal Nerve	Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus	Superior Orbital Fissure, Foramen Rotundum, Foramen Ovale
CN VI	Abducens Nerve	Abducens nucleus	Superior Orbital Fissure
CN VII	Facial Nerve	Facial nucleus, Solitary nucleus, Superior salivary nucleus	Internal Auditory Meatus, Stylomastoid Foramen, Hiatus of Facial Canal, Petrotympanic Fissure
CN VIII	Vestibulococlear Nerve	Vestibular nuclei, Cochlear nuclei	Internal Auditory Meatus
CN IX	Glosspharyngeal Nerve	Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus	Jugular Foremen
CN X	Vagus Nerve	Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus	Jugular Foramen
CN XI	Accessory Nerve	Nucleus ambiguus, Spinal accessory nucleus	Jugular Foramen
CN XII	Hypoglossal Nerve	Hypoglossal nucleus	Hypoglossal Canal

6. Be able to differentiate between sensory ganglia and autonomic ganglia.

Supplementary Materials

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